Came across this blog entry today which seems to cover some really useful Photoshop material, particularly for portrait work. Judging from the number of comments on the page and I am not the only one that thinks this is useful material!
The thing that I find amazing is how difficult many of these tips would be in the traditional darkroom.
http://www.smashingmagazine.com/2008/07/15/70-beauty-retouching-photoshop-tutorials/